The present invention relates generally to a gallium arsenide field effect transistor having an aluminum arsenide or an aluminum gallium arsenide barrier layer.
The following papers are of interest.
(1) S. Swirhun, S. Hanka, J. Nohava, D. Grider, and P. Bauhahn, "Refractory self-aligned-gate, GaAs FET based circuit technology for high ambient temperatures", Proceedings of First International High Temperature Electronics Conference, pp. 295-300, 1991.
(2) K. Fricke, H. L. Hartnagel, R. Schutz, G. Schweeger, and J. Wurfl, "A new GaAs technology for stable FET's at 300.degree. C.", IEEE Electron Dev. Lett., vol. 10, no. 12, pp 577-579, 1989.
S. Swirhun et al at Honeywell have tested FETs fabricated with a self-aligned gate(SAG) process, using dopant implants, isolation implants, tungsten silicide (Wsi) Schottky gates, NiGeNilnNiMo ohmic metal contacts, and SiN passivation. For a 1.1.times.10 .mu.m FET; a drain current on-to-off ratio of about 30:1 was obtained at 350.degree. C. ambient temperature.
K. Fricke et al from West Germany have fabricated FETs grown by metal-organic chemical vapor deposition (MOCVD) using TiPtAu Schottky gates, GEAuNiWSiTiWSiAu ohmic contacts, and SiN passivation. The Fricke device test results are difficult to interpret however, because the results are shown at an estimated temperature and not at the measured ambient temperature. In both the Swihurn and Fricke cases, however, the switching current ratios are inferior by at least an order of magnitude to FETs fabricated with an AlAs buffer layer as in the present invention.
The following United States patents are of interest.
______________________________________ 4,980,325 Berenz 5,026,655 Ohata 4,952,527 Calawa et al 5,084,743 Mishra et al 5,049,951 Goronkin et al 4,916,498 Berenz 4,962,050 Geissberger et al 4,994,868 Geissberger et al 5,300,795 Saunier et al ______________________________________